Production of soft paper products from high and low coarseness fibers

ABSTRACT

Paper products such as bathroom tissue, facial tissue, napkins and paper towels are made from high coarseness fibers such as recycled newsprint fibers, CTMP, TMP, and groundwood. These products exhibit premium level qualities in terms of softness, bulk, and flexibility. The novel process selectively treats these high coarseness fibers in a way that makes the fibers feel softer and enhances papermachine operation with this type of furnish, thereby permitting higher product quality levels than previously possible with high coarseness fibers.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of U.S. patent application Ser. No.08/268,232, filed on Jun. 29, 1994.

BACKGROUND OF THE INVENTION

For each paper making process a correlation exists between fibercoarseness and product quality in terms of product softness or handfeel.Expensive high quality fibers such as bleached northern kraft softwoodfibers are fine, flexible, and produce high quality tissue products. Incontrast, mechanical pulping of softwoods produces coarse, stiff fiberstypically used in making newsprint. Newspapers contain a preponderanceof coarse, high yield fibers, typically stone groundwood (SGW),thermomechanical pulp (TMP), and/or chemithermomechanical pulp (CTMP)fibers. Such coarse newsprint fibers are usually highly refined to causefractures and fibrillations which aid in imparting strength to theresulting newsprint. Such refining changes the "freeness" of the coarsefibers from "high" freeness fibers to "low" freeness fibers. If suchrefined, coarse mechanical fibers are used in a tissue making processthe resulting sheet is not soft, and therefore has poor tissueproperties. A recent thorough discussion of the relationship betweentissue softness and fiber coarseness is contained in Canadian Patent No.2,076,615.

Attempts to produce soft tissue or towel type sanitary paper productsfrom a majority of high yield fibers such as CTMP, TMP or SGW pulp havenot been successful. Likewise, producing soft tissue and towel productsby recycling old newspapers has not been very successful partiallybecause the predominant fiber in newsprint or in old newspapers are lowfreeness, coarse, high yield fibers.

Other complicating factors in producing soft tissue and towel productsby recycling old newspapers are difficulties with the paper machineoperation caused by poor drainage associated with low freeness fibers,and problems caused by high amounts of fines and other substances, whichseparate from the fibers and accumulate in the paper machine watersystem (white water). These materials make it difficult to crepe thetissue sheet from the Yankee drying cylinder, and therefore necessitateoperating the paper machine at conditions which do not promote maximumsoftness.

The present invention solves these difficulties by enzymaticallymodifying the fibers and by adding oils of the type used in newspaperink to the high coarseness fibers, thereby softening the fibers andgiving them release properties which aid in the creping step on thepaper machine. For recycled newsprint, the fibers are enzymaticallymodified, and oils of the types used in newsprint ink are added, and aportion of the printing oils in the fibers are retained, therebysoftening the fibers, and making the fibers more flexible which aids inthe creping step on the paper machine. Consequently, previouslyunachievable levels of tissue and towel softness are possible with thepresent invention using high coarseness fibers or recycled newsprintfibers.

Methods to improve softness of tissue products using low coarsenessfibers by lotionizing the surface of the tissue product have beendeveloped. These methods, however, are applied to the tissue productprior to it being converted into the final product. It would bedesirable to provide a method of achieving these softness gains withoutthe cost and complexity of the current methods.

Conventional recycling of old newspapers to obtain fibers comparable tothe type of fibers used to originally make the newsprint is known in theart as "deinking" and typically involves pulping, washing (usually withsurfactants), screening, centrifugal cleaning, solubilizing insolublecontaminants (usually by strong caustic treatments), washing andbleaching of the fibers to counteract the yellowing effects of caustictreatments.

The first step in conventional recycling of old newspapers is toseparate the paper into individual fibers in water to form a pulpslurry. Surfactants and caustic are added to facilitate thesolubilization and separation of contaminants from the fibers. This isfollowed by removing inks and contaminants from the fibers by acombination of various process steps such as screening, centrifugalcleaning, washing, flotation and the like. The screening and centrifugalcleaning steps remove large contaminants such as paper clips, staples,plastics, etc. The primary purpose of washing and flotation steps is tosuspend contaminants in the water and to remove the contaminants fromthe fibers. When caustic is used to facilitate contaminant removal, someyellowing of the fibers unfortunately occurs due to the caustictreatment. After or during caustic treatment and washing, the fibers areusually bleached (e.g.--with hydrogen peroxide) to counteract theyellowing effect of caustic or to produce better fibers having higherbrightness than the fibers in the original waste paper. Cleaned,decontaminated, and bleached fibers are usually blended with virginfibers and then used in a paper making process for which the fibersproperties are suitable. Because the starting fibers are newsprint typefibers, i.e., coarse, low freeness and low brightness fibers, suchrecycled fibers are most often reused for making blank newsprint. Theyare generally not suitable because of their high coarseness and lowfreeness for making soft tissue products unless blended with a majorityof higher quality fibers such as bleached northern softwood kraft pulp.

Conventional pulping of used newspaper to obtain recycled newsprintfiber is usually done in a high attrition pulper at a consistency of4-8% and at 90° F.-160° F. for 20 minutes to 60 minutes, depending onthe exact type of waste paper being processed. Caustic soda or otheralkaline substances such as sodium silicate are commonly used to raisethe pH of the pulp slurry to pH 9-10 to aid in separating fibers(defibering) and also to loosen the inks and separate dirt from thefiber. At an alkaline pH vegetable oils in the inks are saponified whilemineral oils are emulsified by the combination of alkaline pH, soaps,and surfactants, all of which enhance the removal of oils duringwashing. A surfactant deinking aid (for higher pH ranges) is usuallyadded to further help separate inks from fiber.

The caustic step in recycling processes of old newsprint to obtain wellcleaned quality fibers causes swelling of the fibers, and usuallysolubilizes many components. In addition to saponifying vegetable basedprinting oils, caustic also saponifies natural organic acids typicallypresent in old newspapers to produce the corresponding soaps of thesaponifiable materials. The saponified vegetable oils and organic acidsso formed aid in removal of other contaminants from the fibers, such asnon-saponifiable printing oils (mineral oil). These substances aresubsequently removed from the fibers by washing and/or flotation afterthe caustic treatment.

A major recycler of old newspapers, Garden State Paper, in recentjournal articles, one entitled "The Big "D": Getting Rid of the Ink inRecycled Fiber appearing in the journal Paper Age, 1991 RecyclingAnnual, at pages 23 and 50 and the other article entitled "RecyclingFrom the Newsprint Perspective, at pages 9, 12 and 13 of the same 1991Recycling Annual, (Paper Age, 1991 Recycling Annual) describes itsnewsprint recycling and deinking process as cleaning and screeningfollowed by a series of 3 washings facilitated by the addition ofchemicals to emulsify the printing oils and resins. Again the aim ofthis process is to remove printing ink constituents including oils ascompletely as possible. This is especially important because therecycled newsprint fiber is made into blank newsprint paper which wouldnot have adequate brightness or strength without removing the inkconstituents.

A common component of deinking systems for newspaper waste involvesseparating ink from the fibers and removing the ink typically throughwashing and flotation steps. While conventional alkaline deinkingchemicals are very effective in such deinking, they are known to havethe disadvantage of lowering brightness. Recent research has beendirected to avoiding alkaline deinking chemicals in deinking systems.

Recent developments in wastepaper deinking (U.K. Patent Application2,231,595 published Nov. 21, 1990 entitled "Deinking Water Printed PaperUsing Enzymes" and a North Carolina State University publicationentitled "Enzymatic Deinking of Flexographic Printed Newsprint: Blackand Colored Inks") deal with the use of enzymes to aid in the detachmentand removal of inks from the fibers. These processes describe the use ofenzymes such as cellulase, pectinase, xylanase, and hemicellulases tofacilitate ink removal without the negative effects of caustic treatmenton brightness along with the use of flotation to remove the agglomeratedink particles. Since printing oils are lighter than water, they arereadily removed by flotation treatment particularly in view of thechemicals added to aid in separation. While enzymes are used, thisthorough removal of ink components is counter to the objective of thepresent invention which retains the oils for tissue softness. A paperpresented at the Fifth International Conference on Biotechnology fromMay 27 to May 30, 1992 in Kyoto Japan entitled "Enzyme Deinking ofNewsprint Waste" by John A. Heirmann, Thomas W. Joyce and D. Y. Prasaddescribed research occurring at the department of Wood and PaperScience, North Carolina State University, Raleigh, N.C. That articledescribed the use of acidic flotation deinking systems in which the onlychemicals used were enzymes, calcium chloride and a surfactant. Theenzymes were a preparation containing both cellulase and hemicellulose.Increases in freeness and brightness were noted. However, the importantdistinction is that the acidic flotation deinking system describedremoves ink along with its associated oils which is contrary to thepresent invention.

More recently, high consistency pulping (13-18%) has been utilized forrecycling old newspapers. This type of pulping technology utilizes theadditional effect of rubbing/kneading between the fibers/papers athigher consistency to defiber and assist in separating inks from thefibers. Generally the pulping temperature, time, and chemical additionsare the same as lower consistency pulping described above.

One aspect of the present invention avoids conventional deinking butinstead retains a significant component of the ink, i.e., the printingink oils. The present invention is based on the discovery that if theoily component of ink is not removed from coarse fibers in oldnewsprint, surprisingly high quality, soft tissue products can beproduced. To accomplish this task, a formulation of enzymes is utilizedto loosen a limited amount of the ink constituents for removal and/orredistribution on the fibers. In addition, by avoiding saponificationconditions, e.g. alkaline saponification of fatty acid oils such asvegetable oils, and fiber components such as hemicellulose are notallowed to leach out of the fibers into the paper machine water systemand cause difficulties with the creping operation.

SUMMARY OF THE INVENTION

The present invention provides a method for producing soft tissueproducts by treating the fiber prior to sheet formation. It has beenknown that fiber coarseness is a contributing factor in the productionof soft tissue products. The present invention provides a method ofmodifying high coarseness and low coarseness fibers to improve thesoftness potential of the fibers.

The softness potential of virgin chemical fibers and recycled fibers canbe increased by the addition of vegetable oils, e.g. soya, linseed,castor, safflower, olive, peanut or their fatty acid ester derivatives;mineral oils or lanolin oils and their ethoxylated, acetylated or esterderivatives. The treated fibers are then subjected to appropriatedenzyme and disperser treatment.

Virgin, coarse, high yield fibers (e.g. stone groundwood,thermomechanical and chemithermomechanical pulps) can be made suitablefor producing soft tissue type products by addition of oils typicallyfound in newspaper inks and subjecting the intentionally oil treatedvirgin fibers to appropriate enzyme treatment. Novel fibers and sanitarypaper products containing a majority of enzyme treated coarse, highyield type fibers having oily materials are produced according to thepresent invention. Enzyme treatment utilizes one or more enzymesselected from the group consisting of cellulose, hemicellulose, such asxylanase, and lipase.

The method of making sanitary paper products from virgin or recycledcellulosic fibers disclosed herein comprises:

(a) pulping the cellulosic fibers in water with agitation to produce apulp slurry at a consistency of about 3% to about 18% and a pH belowabout 8.0;

(b) adding to the slurry an enzyme selected from the group consisting ofcellulase, hemicellulose and lipase and maintaining the pulp slurry at atemperature above about 100° F. for at least 15 minutes;

(c) dewatering the pulp slurry to a consistency from about 25% to about35%;

(d) crumbing the dewatered pulp, thereby producing crumbed fibers;

(e) passing the crumbed fibers through a fiber disperser whilemaintaining the fibers at a temperature of about 180° F. and mixingeither a vegetable, mineral or lanolin oil or their derivatives with thefibers; and

(f) using the enzyme treated fibers as a source of fibers in apapermaking process to produce sanitary paper products.

The novel sanitary paper product is made of cellulosic fibers and has abasis weight of between 7 pounds per ream and 40 pounds per ream, aNormalized Tensile Strength (metric) of between 5.0 and 20.0, andcontaining from about 0.2 to 5.0% of an oil selected from the groupconsisting of vegetable, mineral or lanolin oils or their respectivederivatives.

The novel method of modifying cellulosic fibers comprises modifyingcellulosic fiber to improve their tissue and towel making propertiescomprising:

(a) adding about 0.2% to about 5.0% of a vegetable, mineral or lanolinor their respective derivatives to the cellulasic fibers at aconsistency of about 25% or greater, crumbing the fibers, and passingthe crumbed fibers through a fiber disperser while maintaining thefibers at a temperature of about 180° F.

(b) adding to the furnish at a temperature below 140° F., an enzymeselected from the group consisting of cellulase, hemicellulose andlipase and maintaining the pulp in contact with the enzyme andsurfactant at a consistency of between about 3% to about 18% and at atemperature of about 100° F. and about 140° F. for approxiametly 15minutes.

The improved cellulosic fiber for making sanitary paper productsdisclosed herein comprises an enzyme modified cellulosic fibercontaining bewtween about 0.2% and about 5.0% of an oil selected fromthe group consisting of a vegetable, mineral or lanolin or theirrespective derivatives.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically shows the relationship between fiber coarseness andtissue softness conventionally obtained by lightweight, dry crepe tissuemaking processes and the superior results obtained by the presentinvention.

FIG. 2 is a tabular presentation of the experimental results of examples1 and 2. In addition, FIG. 2 incorporates the experimental results ofU.S. patent application Ser. No. 08/268,232, filed on Jun. 29, 1994.

FIG. 3 is a tabular presentation of the difference in response betweenthe use of a castor oil and a mineral oil.

FIG. 4 is a tabular presentation of a control sample with and withouttreatment.

DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENT

The present invention is based upon the discovery that high yield typecellulosic fibers (i.e. fibers produced by predominantly mechanicalseparation of wood fibers and typically containing at least 80% byweight of the source material) can produce very soft tissue typeproducts having product qualities comparable to tissue products madefrom expensive bleached northern softwood kraft fibers. These cellulosicfibers include high coarseness fibers having a coarseness of greaterthan 17 mg/100 meters, and low coarseness fibers having a coarseness ofless than 17 mg/100 meters. Particularly, soft tissue type products canbe produced from these types of cellulosic fibers by adding an oilselected from a group consisting of mineral oils, vegetable oils,lanolin oils, and cosmetic type oils.

Prior to adding these oils the cellulosic fibers are subjected to anenzyme treatment. Soft paper products are then made with the oil treatedand enzyme modified fibers. It is critical in the practice of thepresent invention that a sufficient quantity of oils be on or in thefibers prior to making tissue or other types of sanitary paper products(e.g. towels, napkins and facial tissues) from such fibers.

Soft tissue type products can also be produced from old newspapers (ONP)by retaining certain oil materials typically found in used newspapers,subjecting the used newspaper fibers containing such oils to an enzymetreatment and making paper with such oil and enzyme modified fibers. Itis critical in the practice of the present invention that a sufficientquantity of oils typically found in used newspapers be on or in thefibers prior to making tissue or other types of sanitary paper products(e.g. towels, napkins and facial tissues) from such fibers. Furthermore,if the oil is removed during deinking or not present as with virginfibers, the oil can be added to the fibers and the fibers containingsuch oils can then be subjected to an enzyme treatment prior to makingsanitary paper products from the oiled and enzyme modified fibers toobtain the benefits of the present invention.

Vegetable oils and mineral oils are typically used in newspaper printinginks and are found in used newspapers, generally as components of theprinting inks. In order to retain oil components of used newspapers,conventional repulping and deinking process must be modified. Thepreferred modification of conventional deinking is to eliminatesaponification conditions in which vegetable type oils (or any oilcontaining an ester group) are converted into soaps. However, if theoils, are removed during deinking, they can be replaced with an oilselected from the group consisting of vegetable, mineral or lanolin oilsor their derivatives prior to enzyme treatment.

In one embodiment, the method of the present invention employs virgincellulosic fibers as a starting material. The virgin cellulosic fibersare pulped to produce a slurry having a consistency between about 3% toabout 18% and a pH below about 8. The slurry is then treated with asurfactant and an enzyme such as a cellulase, xylanase or lipase or acombination of such enzymes at a temperature above about 100° F. for atleast 15 minutes. After the enzyme is added, the slurry is dewatered toa consistency from about 25% to about 35%. The dewatered slurry is thencrumbed, thereby producing a crumbed fiber. The crumbed fiber is thenpassed through a fiber disperser and mixed with an oil selected from thegroup consisting of vegetable, mineral or lanolin oils or theirderivatives up to the point where the final paper product will still beabsorbent and aesthetically appealing. Preferably, about 0.2% to about5.0% of the selected oil is mixed while maintaining the fibers at atemperature of about 180° F. The slurried enzyme treated pulp is thenused as a source in conventional sanitary paper manufacturing process,preferably a tissue papermaking process. If it is necessary to conduct ascreening, cleaning, flotation and/or some washing of the pulp slurryprior to using it as a furnish for making sanitary paper products (e.g.tissue, towel, facial tissues or napkins), it is important that asubstantial quantity of the oily contaminants be retained on the pulpafter such screening, cleaning, flotation and/or washing steps, or elsereplaced prior to enzyme treatment and papermaking to achieve thedesired softness and aesthetic levels.

The pulping process of the present invention when using either virginhigh coarse or low coarse fibers preferably involves pulping the fibersat 6-9% consistency and an elevated temperature, preferably about 120°F.-180° F. The fibers are pulped continuously for a time sufficient todefiber the pulp and prepare it for reaction with the enzyme and/orsurfactant mixture. Preferably the fiber is pulped for about 15 to 60minutes. The slurry is then transferred to a holding chest/blend wherethe pH is adjusted to a temperature and pH level sufficient for reactionwith the enzyme and/or surfactant mixture. The preferred temperatureconditions is about 120° F.-140° F. with a pH of between 4 and 7.Surfactant and enzymes are then added to the pulp slurry and allowed toreact with the fibers for a reaction period of about 15 minutes to about30 minutes to complete the treatment. The pH is then adjusted to about7, and the pulp is dewatered through a press, such as a commerciallyavailable Andritz press, to a consistency about between 25% to about35%. The dewatered pulp is then crumbed using a commercially availablecrumbing apparatus, such as that from Scott Equipment Co., New Prague,Minn., to produce a crumbed fiber. The crumbed fiber is then passedthrough a fiber disperser such as a commercially available Micar,manufactured by The Black Clawson Company, Middletown, Ohio, and mixedwith oil selected from the group consisting of vegetable, mineral orlanolin oils or their derivatives while maintaining the fibers at atemperature of about 180° F. The micar is situated so that it is capableof (1) injecting steam so that the fiber maintains a temperature ofabout 180° F., (2) and so that the selected oil can be mixed with thecrumbed fibers. The amount of oil added and mixed will vary from about0.2% to about 5.0% depending on the weight of the dry fiber. The fiberare the maintained at a temperature sufficient to allow the oils to beretained in or on the fiber. The fiber temperature is preferablymaintained at about 180° F. by injecting steam when the selected oil ismixed with the fibers. Additional screening is unnecessary with thevirgin fibers, although screening and/or centrifugal cleaning may bepracticed to remove any large contaminants to protect the papermachine.Optionally, limited washing of the enzyme treated and oil containingpulp can be done on the papermachine by using the unwashed pulp in apapermaking furnish on a papermachine.

Preferably the slurry and enzyme treatment steps when using virgincellulosic fibers or old newspapers is the same. This treatment isconducted in several stages beginning with slurrying the cellulosicfibers or newsprint at a consistency of between about 3% and 18% with orwithout surfactant, and preferably at a temperature of the pulp slurrybetween about 100° F. and 180° F. and maintaining the elevatedtemperature for at least about 15 minutes. This is followed by adjustingthe pH and reducing the temperature of the pulp slurry to a temperatureand pH suitable for maintaining active enzyme conditions. Preferredenzyme treatment conditions are a pH of 4 to 7 and a temperature belowabout 140° F. and preferably above about 100° F. If pulping of thevirgin coarse fibers or newspapers is performed under conditions alsosuitable for enzyme treatment, pulping and enzyme treatment steps can becombined.

When pulping and enzyme treatment are combined into a single step, theenzyme with or without the addition of a surfactant, can be added to thewater either prior to or after addition of the virgin fibers ornewspapers for pulping. Optionally, a surfactant of the type typicallyused in contaminant removal in newsprint recycling processes is added tothe pulp slurry. One or more enzymes can be used. Enzymes are preferablyselected from the group consisting of cellulase, xylanase and lipase.The pulp is maintained in contact with the enzyme for at least about 15minutes and preferably about 30 minutes.

When using virgin high coarse or low coarse fibers, newsprint, or oldnewspapers, a critical component in the above process sequence is havingoil selected from the group consisting of vegetable, mineral or lanolinoils or their derivatives in contact with the enzyme treated fibers andretained with (on or in) the fibers during papermaking. Without beingbound thereby, our theory by which virgin high coarse and low coarsefibers become very suitable for making soft tissue type sanitary paperproducts is that some interaction between the fibers, oils and enzymesoccurs that is enhanced by the presence of a surfactant. Thisinteraction synergistically improves the tissue making properties of thecoarse fibers.

Other oils that may be employed in accordance with the present inventioninclude vegetable oils, e.g. soya, linseed, castor, safflower, olive,peanut or their fatty acid ester derivatives; mineral oils or lanolinoils and their ethoxylated, acetylated or ester derivatives.

Dyes

Recycled newsprint fibers of the present invention retain inkycontaminants and are therefore a light gray color. Tissue products madewith a majority of such fibers are preferably dyed to a more pleasantcolor. The dyes useful in this invention must be water soluble andbecause of the difficulty of uniformity dying oily contaminated fibers,the dyes should be substantive to cellulosic fibers. They should also becationic, i.e. they will form positively--charged colored cations whendissociated in water. These dyes are particularly well suited for dyeingmechanical and unbleached chemical pulps. Such pulp fibers contain asignificant number of acid groups, with which the positively-chargedcations can react by salt formation. These dyes can be selected fromamong the basic dyes, a group well known from prior art, in which thebasic group is an integral part of the chromophore, or from the newerclass of cationic direct dyes, in which the basic group lies outside ofthe molecules resonance system. The dye is preferably added in amountsranging from 0.01% to 3%, most usefully, at 0.05 to 0.5% of the weightof air dry fiber.

These dyes can be applied at any normal papermaking pH, either acidic orneutral. Their excellent affinity for unbleached fibers allows them tobe added to the papermaking system as late as the inlet to the fan pump,but a longer residence time, e.g., introduction at the suction side ofthe machine chest transfer pump would be preferred. In either case athick stock location with good mixing is desirable.

Enzymes

Suitable enzymes for use in the present invention should be selectedfrom the group consisting of cellulase, hemicellulase (e.g. xylanase),or lipase enzymes and preferably one of each type is used incombination. Each type of enzyme functionally targets differentcomponents of used newspaper fibers and/or contaminants usuallyassociated with such fibers. Cellulase enzymes contribute to ink removalby attacking the cellulose component of fibers in the proximity of ink.Xylanase and other hemicellulases attack hemicellulose components offibers for brightness enhancement while lipase attacks resins in thefibers and in the ink formulations. When all three types of enzymes areused together a synergism results, that achieves better ink removal aswell as eliminating so called "stickies". Stickies are a well knowncontaminant in used paper resulting from adhesives, pressure sensitivelabels, etc. and are known to cause papermachine runability problems. Amixture is preferably selected of enzymes that will attack the printedwaste paper in a way that enhances tissue softness and modifiescontaminants so that they do not hurt papermachine operation. Also,enzyme treated pulp in accordance with the present invention willimprove paper machine running ability and produce a superior product atlow costs.

Hemicellulase is a general term describing various types of enzymes eachdegrading specific types of compounds commonly known as hemicellulaseand found in wood and other plant materials. Xylanase is the preferredhemicellulase enzyme because it is active toward the xylan, a commontype of hemicellulose. The constituents of hemicellulose differ fromplant to plant. The most abundant of the wood hemicelluloses are thexylans, which are polymers of 1,4-linked β-D-xylopyranose units some ofwhich bear short side chains such as 1,3-linked α-1-arabinofuranoseunits or esterified 1,2-linked α-d-glucuronic acid units. Alsoimportant, particularly in softwoods, are 1,4-β-D-glucomannans withrandomly distributed glucose and mannose units, bearing side chains suchas 1,6-linked α-D-galactopyranose units. Hemicellulose differs fromcellulose in three important respects. In the first place they containseveral different sugar units whereas cellulose contains only1,4-β-D-glucopyranose units. Secondly they exhibit a considerable degreeof chain branching, whereas cellulose is a strictly linear polymer.Thirdly, the degree of polymerization of native cellulose is ten to onehundred times greater than that of most hemicelluloses. The term"hemicellulase" refers to any specific enzyme class that reacts with aspecific hemicellulose and as such, hemicellulase is not a specificenzyme class but a generic term of art for a group of enzyme classes.Xylanase is a specific enzyme class that attacks xylan and thereforexylanase falls within the general term "hemicellulase."

Many types of enzymes could be used within classes of enzymes known ascellulase, xylanase (or other hemicellulase) and lipase. Cellulase hasthe most commercial choices available because it comes from manydifferent sources, such as from Aspergillis niger, Trichoderma reesei,T. viride, T. koningi, F. solani, Penicillium Dinophilum, P.funiculosum. It is preferred to use a cellulase that poses endo-exoglucanase functionality to attack both amorphous and crystalline regionsof cellulose so that the enzyme can attack any place on the cellulosicsurface where ink is attacked.

The preferred cellulase is a product sold under the trademarkCelluclast® 1.5 L, by Enzyme Process Division, Bioindustrial Group, NovoNordisk A/S, Novo Alle, 2880 Bagsvaerd, Denmark. Celluclast 1.5 L is aliquid cellulase preparation made by submerged fermentation of aselected strain of the fungus "Trichoderma reesei." The enzyme catalyzesthe breakdown of cellulose into glucose, cellobiose and higher glucosepolymers. The relative amounts of reaction products formed depend on thereaction conditions. Celluclast 1.5 L has an enzyme activity of 1500NCU/g and is a brown liquid with a density of approximately 1.2 g/ml.Activity is determined on the basis of Novo Cellulase Units (NCU). OneNCU is the amount of enzyme which, under standard conditions, degradescarboxy methylcellulose to reducing carbohydrates with a reduction powercorresponding to 1 micromole (umol) glucose per minute. Standardconditions are: Substrate--carboxymethyl-cellulose (CMC Hercules-7LFD);Temperature--40° C.; pH--4.8; Reaction time--20 minutes.

Xylanase can be obtained from a source such as A. pullulans, orStreptomyces lividans, or Streptomyces roseiscleroticus. Its purpose isto attack the xylan portion of the lignocellulose fiber which isconsidered to link the white colored cellulose with the brown coloredlignin. Therefore, the attack on xylan hemicellulase enhances theremoval of lignin, thus making the fiber brighter. It is not necessarythat the xylanase be cellulase free or from any particular bio-source.In this respect, mushroom enzyme (multiple enzymes found after mushroomgrowing) could be used without purification.

One preferred xylanase enzyme is Pulpzyme® HA which is a xylanasepreparation derived from a selected strain of Trichoderma reeseiavailable from Enzyme Process Division, Bioindustrial Group, NovoNordisk A/S, Novo Alle, 2880 Bagsvaerd, Denmark. Pulpzyme® HA containsendo-1,4-beta-D-xylanase (EC 3.2.1.8) as well as exo-1,4-beta-D-xylanase(EC 3.2.1.37) activities. Pulpzyme® HA has a certain amount of cellulaseactivity in addition to its xylannase activity.

Pulpzyme® HA is a brown liquid preparation of a xylanase having anactivity of 500 XYU/g and containing approximately 300 endo-glucanaseactivity units (EGU/g). One xylanase activity unit (XYU) is defined asthe amount of enzyme which under standard conditions (pH 3.8, 30° C., 20min. incubation) degrades larchwood xylan to reducing carbohydrates witha reducing power corresponding to 1 umol xylose. One endo-glucanase unit(EGU) is defined as the amount of enzyme which under standard conditions(pH 6.0, 40° C., 30 min. incubation) lowers the viscosity of acarboxymethyl cellulose solution to the same extent as an enzymestandard defining 1 EGU. Pulpzyme® HA has a very low activity towardscrystalline cellulose. Another preferred xylanase is Pulpzyme® HB whichis a xylanase preparation derived from a selected strain of bacterialorigin. It is available from Enzyme Process Division, BioindustrialGroup, Novo Nordisk A/S, Novo Alle, 2880 Bagsvaerd, Denmark. It containsendo-1,4-beta-D-xylanase activity (EC 3.2.1.8), and is virtually free ofcellulase activity. Pulpzyme® HB is commercially available as a brownliquid preparation, having an endo-xylanase activity of 600 EXU/g inwhich one endo-xylanase activity unit (EXU) is defined as the amount ofenzyme which, under standard conditions (pH 9.0, 50° C., 30 min.incubation), degrades RBB xylan.

Lipase can come from Pseudomonas fragi, Candida cylindricea, Mucorjavanicus, Pseudomonas fluorescens, Rhizopus javanicus, Rhizopusdelemar, Rhizopus niveus, and various species of Miehei, Myriococuum,Humicola, Aspergillus, Hyphozyma, and Bacillus. These have both lipaseand esterage activities, and they are known to degrade triglyceride inwood resin into glycerol and fatty acids. As such the lipase enzymescould attack the vegetable oil component of the ink directly. Theglycerol by product of lipase activity could help to make the cellulosesofter.

Preferred lipase enzyme is Resinase® A 2X, which is a liquid lipasepreparation for the hydrolysis of ester constituents of wood resin.Resinase® A 2X is commercially available from Enzyme Process Division,Bioindustrial Group, Novo Nordisk A/S, Novo Alle, 2880 Bagsvaerd,Denmark as a brown liquid preparation with an activity of 100 KLU/g. Thelipase activity is measured in Kilo Lipase Units (KLU). One KLU is theamount of enzyme activity which liberates one millimole butyric acid perminute from an emulsion of tributyrin at a temperature of 30° C. and apH of 7.0. The analysis is made in a pH-stat system in which theliberated acid is titrated continuously by addition of sodium hydroxide.The enzyme is not substrate-limited during the analysis.

Other enzymes could also be used in combination with these three typesof preferred enzymes. They are ligninase, laccase, pectinase, proteaseand mannanase. Also, enzymes could be obtained from DNA altered andengineered microorganisms which express more of specific enzymes or morevolumes to get better economy.

The preferred amount and combination of enzymes is 1.33 kg.cellulase/ton(2,000 lbs) of pulp for cellulase, 0.33 kg. xylanase/ton, and 0.33 kg.lipase/ton. As low as 0.25 kilograms of enzymes per ton of pulp (kg/ton)to as high as 25 kg/ton of pulp can be used as the total amount of allenzymes. However, 1 to 3 kg/ton total of all enzymes is a particularlypreferred usage rate. The preferred range for each enzyme is: cellulase,0.25 to 10, kg/ton; xylanase, 0.05 to 2.5, kg/ton; and lipase, 0.05 to2.5, kg/ton.

Swelling of the fiber structure improves the enzyme action by assistingthe penetration of the large enzyme molecules into the fiber. Elevatedtemperature (e.g. above ambient and below 140° F.), use of surfactant,and acid or mild alkaline chemicals can be used in pulping the newsprintto physically open up the lignocellulosic fiber structures so thatenzymes can better penetrate the structures and perform their respectivefunctions. If high pulping temperatures are used e.g. above about 140°F., the temperature must be lowered to a temperature suitable for enzymetreatment before the enzymes used are added. For most enzymes, thesuitable temperature is less than about 140° F.

Surfactant Use with Enzyme Treatment

A synergistic result is obtained with the combination of a surfactantand an enzyme. The minimum effective amount of surfactant to obtainsynergy, is the amount needed to open up the fiber rather than thehigher levels used for solubilizing oils by emulsifying the oilycontaminants. The preferred amount of surfactant is from about 0.025% toabout 0.1% based on the weight of fibers. Nonionic surfactants arepreferred for addition to the enzyme treatment step to improve theenzymatic action for a better handfeel improvement. A preferred nonionicsurfactant is commercially available as DI600® from High Point ChemicalCorp. DI6000 is an alkoxylated fatty acid, nonionic surfactantspecifically developed for flotation type deinking of newsprint. Othernonionic surfactants well known in the art of deinking could be used,such as: Alkyl phenyl ether of polyethylene glycol, e.g. Union Carbide'sTergitol® series of surfactants; alkylphenolethylene oxide condensationproducts, e.g. Rhone Poulenc, Incorporated's Igepal® series ofsurfactants; aryl alkyl polyether alcohol, e.g. Rohm and Haas's Triton®X 400 series of surfactants such as Triton X-100. In some cases ananionic surfactant may be used depending on the contaminants present inthe wastepaper. Examples of suitable anionic surfactants are: ammoniumor sodium salts of a sulfated ethoxylate derived from a 12 to 14 carbonlinear primary alcohol such as Vista's Alfonic® 1412A or 1412S; and,sulfonated naphthalene formaldehyde condensates, e.g. Rohm and Haas'sTamol® SN. In some cases, a cationic surfactant can be used, especiallywhen debonding is also desired. Suitable cationic surfactants includeimidazole compounds e.g., CIBA-GEIGY's Amasoft® 16-7 and Sapamine® Pquaternary ammonium compounds; Quaker Chemicals' Quaker® 2001; andAmerican Cyanamid's Cyanatex®.

Oil Types

Oils of the type typically used in printing, particularly printing ofnewspapers and in the formulation of ink for such printing, are suitablefor practice in the present invention. Mineral oils and vegetable oilsare the most common types of oils used in formulating printing inks fornewspapers. Mineral oil, also known-as white mineral oil, alboline,paraffine, Nujol, Saxol, and lignite oil, is generally classified as CAS#64742-46-7. While historically such oils may have been derived fromvarious sources, commercially they are typically a petroleum distillatefraction with a carbon chain averaging from about 10 to about 14 carbonatoms and usually a mixture of paraffinic hydrocarbons, napthenichydrocarbons and alkylated aromatic hydrocarbons. Such oils have aspecific gravity of about 0.8 to about 0.85, a viscosity at 100° F. of38-41 SSU (Saybolt Universal Units) and an initial boiling point ofabout 500° F. (260° C.). Vegetable oils of the type typically used informulating printing inks can be derived from various sources. Typicalis an oil derived from soy beans known as Soya oil, Chinese bean oil,soy bean oil, or just plain soy oil with a chemical abstract servicedesignation CAS #8001-22-7. Such oils are saponifiable with asaponification value of about 185 to 195, a solidifying point of about5° F. to about 18° F., a melting point of about 70 to about 90° F. andan Iodine value of about 135 to 145. Other vegetable sources of oil andother types of oil suitable for use in printing inks can also be used inthe practice of the present invention.

Oil Content

The amount of oil that should be on the fibers (whether on the surfaceor within the structure of the cellulosic fibers) should be from about0.2% to about 2%. When newspaper is being used, then preferably this oilcontent is obtained by not saponifying or solubilizing oils on usednewspapers during pulping and treating the used newspapers and preparingthem for use in a papermaking furnish. It is also preferred that asurfactant, if used, be used in moderation so as not to wash off oilswhile preparing newsprint for use in a papermaking furnish for sanitarypaper products. When virgin fiber is being used the oil can be added tovirgin fibers by either adding oil onto the pulp prior to slurrying, byadding the oil into a water slurry of the fibers so that the oil comesin contact with the fibers prior to subjecting the fibers to enzymetreatment in accordance with the disclosure herein, or preferably byinjecting or mixing oil with the fibers in the fiber disperser. In itsbroadest concept, the invention requires the presence of oils on or inthe fibers from about 0.2% to about 5.0%.

While the synergistic effect is obtained with oils and enzyme treatmentof cellulosic fibers, it is most beneficial to high yield fibers, othercellulosic fibers would have their sanitary qualities enhanced by theprocess of the present invention so that softer more flexible sanitarypaper products could be made from such fibers. Such fibers include bothnorthern and southern softwood and hardwood kraft, both bleached andunbleached, bleached and unbleached sulfite fibers in addition to thebleached and unbleached high yield fibers such as stone groundwoodfibers, thermomechanical fibers and chemithermomechanical pulp fibers.Specific examples of such fibers are: bleached softwoodchemithermomechanical pulp (SWCTMP); bleached northern softwood kraft(NSWK); bleached recycled fiber (RF); bleached eucalyptus kraft pulp(BEK); bleached southern softwood kraft (SSWK); and bleached hardwoodchemithermomechanical pulp (HWCTMP).

The oil containing and enzyme treated fibers of the present inventioncan be used in conventional papermaking processes for the production ofsanitary paper products including toilet tissue grade paper, facialtissue grade paper, paper towels and paper napkins in accordance withany conventional process for the production of such products. Thesoftness and bulk of such products would be improved by the use of oilcontaining and enzyme treated fibers of the present invention. Becauseof the bulk improvements, paper towels produced with fibers of thepresent invention would be enhanced.

In accordance with the present invention, it has been discovered thatconventional deinking is counterproductive to making of soft tissueproducts from used newspapers because it removes oil that can bebeneficial to softness of tissue and towel products. The presentinvention is also based on the discovery that oil of this type used innewsprint is beneficial to softness of tissue and towel products.Softness is difficult to measure or quantify for tissue products becausesoftness is perceived by the user by handfeel which is influenced bysmoothness and other surface characteristics in addition to sheetpuffiness. Handfeel tests have been developed and handfeel data reportedherein has been obtained using the following test:

Handfeel Test

Scope

Several different lightweight, dry crepe tissues for use as standardswere produced from commercially available pulp of differing qualitiesfor imparting softness to tissue products and were used to define anumerical softness scale. A numerical value was assigned to the softnessof each tissue standard. The softest product was assigned a handfeelvalue of 86, and was a lightweight, dry crepe tissue produced with 50%Irving northern softwood kraft fibers and 50% Sante Fe Eucalyptus kraftpulp. The harshest product for use as a standard was produced with 100%bleached softwood chemithermomechanical pulp, (SWCTMP) and was assigneda handfeel value of 20 on the scale. Other lightweight, dry crepe tissuesamples for use as standards in defining the "Handfeel Softness" scaleand having softness qualities between the softest and harshest tissuestandards were produced from different pulp or pulp blends and wereassigned handfeel softness values between 20 and 86. The pulps used arefurther described in the following paragraphs. Pulp blends and fibercoarseness of the pulp blends used to produce additional tissuestandards are given in Table III along with the tensile strength of eachtissue standard. Tissue manufacturing processes other than thelightweight, dry crepe process and other pulp fibers than those used toproduce the standards are capable of producing tissue products outsideof the 20 to 86 handfeel softness scale defined by tissue standardsdescribed herein. However, for the purpose of establishing theimprovement in softness achievable with the present invention, the abovedefined handfeel softness range of 20 to 86 for lightweight, dry crepeproducts is accurate and sufficient for comparative purposes. Recyclednewsprint fibers of the present invention could produce tissue productshaving softness values higher than 86 when used in other tissue makingprocess such as the through-dried process or when blended with otherfibers.

Pulps Used To Produce Handfeel Standards

(a) Bleached softwood chemithermomechanical pulp (SWCTMP) (Temcell grade500/80) having a Canadian Standard Freeness (CSF) of 500 and an ISObrightness of 80 was made from Black spruce and Balsam fir. Pulping waswith sodium sulfite pretreatment and pressurized refining followed byalkaline peroxide bleaching to 80° ISO brightness. Kajaani coarseness ofthe fibers equaled 27.8 mg/100 meters and the Kajaani weight averagefiber length was 1.7 mm.

(b) Bleached northern softwood kraft (NSWK) (Pictou grade 100/0-100%softwood) was made from Black spruce and Balsam fir. Pulping was by thekraft process to Kappa#=28 followed by CE_(o) DED bleaching to 88° ISObrightness. Kajaani coarseness equaled 14.3 mg/100 meters and Kajaaniweight average fiber length was 2.2 mm.

(c) Bleached recycled fiber (RF) was made from sorted mixed office wastethat was pulped, screened, cleaned, and washed to 550° CSF followed bybleaching with sodium hypochlorite to 80° ISO brightness. Kajaanicoarseness equaled 12.2 mg/100 meters and Kajaani weight average fiberlength was 1.2 mm.

(d) Bleached eucalyptus kraft pulp (BEK) (Santa Fe elemental chlorinefree grade) was made from Eucalyptus Globulus pulped to Kappa#=12 by thekraft process followed by ODE_(o) D bleaching to 89° ISO brightness.Kajaani coarseness equaled 6.8 mg/100 meters and Kajaani weight averagefiber length was 0.85 mm.

(e) Bleached southern softwood kraft (SSWK) (Scott Mobile pine) was madefrom Loblolly and Slash pine and pulped to Kappa#=26 followed by CEHEDbleaching to 86° ISO brightness. Kajaani coarseness equaled 27.8 mg/100meters and Kajaani weight average fiber length was 2.6 mm.

(f) Bleached Hardwood Chemithermomechanical Pulp (HWCTMP) (MillarWestern grade 450/83/100) having a Canadian Standard Freeness (CSF) of450 and an ISO brightness of 83 was made from quaking aspen. Pulping waswith alkaline peroxide pretreatment and pressurized refining followed byalkaline peroxide bleaching. Kajaani coarseness of the fibers equaled13.8 mg/100 meters and the Kajaani weight average fiber length was 0.85mm.

Apparatus

The test method requires no apparatus. The test method uses theprocedures and materials described below to evaluate tissue samplesusing a panel of ten or more people and rank softness of the samples onthe softness scale using the product standards of known softness scalevalues.

Sample Preparation

1. Five samples to be tested by the panel of evaluators (judges) shouldbe selected.

2. Calculate the number of sample pads and pads of standard samplesneeded for the test panel of judges for each product to be evaluated forsoftness using the following equation:

Pads needed (each product)=(x-1)x(y)

x=number of products to be tested

y=number of persons on the test panel

3. Randomly select a roll of sample tissue for each product beingevaluated and discard the first few sheets (to get rid of the tail tyingglue).

4. Prepare sample pads from each roll of product being tested. Each padshould be 4 sheets thick and made from a continuous sample of tissuethat is four sheets long. Each pad is made as follows: the four sheetlong sample is first folded in half. This results in a double thicknesssample that is 2 sheets long. The double thickness sample is then foldedin half again to produce a 4 sheet thick, single sheet long sample pad.The folding should be done so that the outside surface of the sheetswhen it was on the roll of tissue becomes the outside surfaces of thepad. If a product being tested is "two-sided", that is it has differentsurface characteristics on the outside surface of the sheet versus thesurface facing the inside of the roll then the product should be testedtwice, once with the surface facing the outside of the roll as the outersurface of the sample pad and also tested with a separate sample padprepared in which the folding results in the sheet surface facing theinside of the roll becoming the outer surface of the sample pad.

5. Make up the required number of pads from each product using theformula in paragraph 2 above. If more than one roll of a product isneeded no prepare the required number of pads, then it is important thatstacks of pads be randomized with product from each of the rolls. Codeeach pad with the batch code in the top left hand corner (on the fold).

6. Select three standards to be used as references by the panel fromamong the standard tissues as follows:

Select the coarsest sample being evaluated and compare it to standardtissue sample pads and select a lower standard that is slightly coarserthan the coarsest sample.

Select the softest sample of product being evaluated and select astandard tissue pad that is slightly higher (softer) than the softestsample being evaluated.

Select a third standard which falls approximately in the middle of thelower and higher standards selected.

The three standard tissue pads selected become the handfeel referencesfor the panel and define the softest, coarsest and midrange.

7. The handfeel references bracket the softness range of the productsbeing evaluated by the panel. For greater accuracy, the highest andlowest references selected should be approximately 30 points apart onthe Handfeel Softness Scale. The middle reference should be eight ormore points apart from the lower and higher references.

Panel Member Selection and Instruction

1. Select a panel of about 10 people having about the same number ofmales and females and with age variations.

2. Ensure the panel members understand the instructions and ifnecessary, give a "trial run".

3. Panels should be conducted in a quiet location.

Test Procedures

1. Begin the softness test by reading the following StandardInstructions.

Standard Instructions

These instructions are to be read to each panel participant beforebeginning the softness panel test procedure.

a. Purpose

"The purpose of this procedure is to compare the softness of toilettissue samples."

b. Method

"You will be given two sample pads of toilet tissue at a time. Comparethe two to each other using your dominant hand and make the comparisonby feeling each sample with your dominant hand. You may stroke, bend, orcrunch the samples as you see fit for making your judgment."

c. First Decision

"After feeling each of the two sample pads pair, you are asked to decidewhich sample is softer."

d. Second Decision

"Rate the degree of difference in softness between the two pads usingthe following rating:

The scale uses odd numbers 1, 3, 5, 7, 9. You may use even numbers ifyou feel that the numbers listed do not fully represent the differencebetween two products."

Panel Rating Scale ##STR1##

e. Calibration

"Before we start I will give you an example of the softest standard tobe used for comparison and a sample pad of the least soft (coarseststandard) products. Please handle both. The difference in softness youfeel between the two standard references you will rate on the definitionscale as 9." (The 9 on the rating scale is the equivalent to the numberof handfeel points on the softness scale between the higher and lowerreferences selected for the panel in step 6.)

f. Participant Reaction

"Do you have any questions about the test procedure?"

g. Reassurance

"Finally, don't agonize too long over each decision. Your opinion is asgood as anybody else's. There are no right or wrong answers!"

2. Present every combination of sample pads and reference pads to eachpanel member and ask them to select the preferred sample and then rankthe difference using the 1 to 9 rating scale of softness. Each panelmember should receive the pairs in random order to avoid sequenceerrors.

3. Record the results of each pair as XYn. Where X is the preferredsample code, Y is the non-preferred sample code and n is the scale value(1 to 9).

Data Analysis

The paired comparison results are treated as if they belong to a ratioscale. The definition of a ratio scale is given as follows: A scale is aratio scale if this scale is invariant under positive lineartransformations of the form y=ax, a>0.

The data pairs and ratio weights for "n" number of pads are loaded intoa square matrix A of the following form.

    ______________________________________                                                0.sub.1 0.sub.2    . . .    0.sub.n                                   ______________________________________                                        0.sub.1   W.sub.1   W.sub.1 W.sub.1                                                     W.sub.1   W.sub.2 W.sub.n                                           0.sub.2   W.sub.2   W.sub.2 W.sub.2                                                     W.sub.1   W.sub.2 W.sub.n                                           0.sub.n   W.sub.n   W.sub.n W.sub.n                                                     W.sub.1   W.sub.2 W.sub.n                                           ______________________________________                                    

Where O_(i) are the individual samples and W_(i) are the scale values(ratio weights) for each pair.

For square matrices of this type the following property exists

    AW=MW

Where W=(W₁, W₂, . . . W_(n)). The weight vector W is the eigne vectorof the matrix A corresponding to its eigne value n. Saaty has shown(See, Saaty, T. L. "A Scaling Method for Priorities in HierarchicalStructures", Journal of Mathematical Psychology, 15, 234-281 (1977) andSaaty, T. L., "Measuring the Fuzziness of Sets", Journal of Cybernetics,4(4), 53-61 (1974)) that to extract the eigne vector W from theestimated weights requires finding the largest eigne value of A (λ max).A computer program to solve for λ max and W is provided in McConnell,Wes, "Product Development Using Fuzzy Sets", INDA Tenth TechnicalSymposium, pp 55-72, Nov. 17-19, 1982. The resulting eigne vector W isthe best estimate ratio scale of the paired inputs. Taking the log ofeach element in this vector creates the more familiar equal intervalscale in which the distances between objects are linear. The standardsoftness values are plotted versus the estimated equal interval scalevalues and the unknown samples are assigned numerical values byinterpolation.

The mean and standard deviation of the standard softness values of eachunknown sample are calculated from the calculated standard softnessvalues for all panel members. If any individual panel member value fallsoutside of 2 standard deviations from the mean, that value is discardedand the mean and standard deviation are recalculated. The mean of thestandard softness values with no values outside of 2 standard deviationsfrom the mean is the standard handfeel softness value for that unknownsample. ##STR2##

Tensile Strength

Tensile strength values given herein for tissue type paper products aremeasured by a breaking length test (TAPPI Test Method No. T494om-88)using 5.08 cm. sample span and 5.08 cm/minute cross head speed.Typically, tissue strengths are different in the machine directionversus cross machine direction of the sheet. Also, the basis weight oftissue samples vary which affects tensile strength. In order to bettercompare tensile strengths from various tissue samples it is important tocompensate for the differences in basis weight of the samples and formachine directional differences in tensile strength. This compensationis achieved by calculating a "Basis Weight and Directionally NormalizedTensile Strength" (hereinafter "Normalized Tensile Strength" or "NTS").NTS is calculated as the quotient obtained by dividing the basis weightinto the square root of the product of the machine direction and crossmachine direction tensile strengths. Tensile strength calculationsnormalized for differences in basis weight and machine direction havebeen devised for better comparisons of tissue samples. Tensile strengthsare measured in both the machine direction and cross machine directionand the basis weight for the tissue sample is measured in accordancewith TAPPI Test Method No. T410om-88. When English units of measurementare used, tensile strength is measured in ounces per inch and basisweight in pounds per ream (2880 square feet). When calculated in metricunits the tensile strength is measured in grams per 2.54 centimeters andthe basis weight is measured in grams per square meter. It should benoted that the metric units are not pure metric units because the testapparatus used for testing tensile is set up to cut a sample in inchesand accordingly the metric units comes out to be grams per 2.54centimeters. Using the abbreviations MDT for machine direction tensile,CDT for cross machine direction tensile and BW for basis weight, themathematical calculation of Basis Weight and Directionally NormalizedTensile strength (NTS) is:

    NTS=(MDT×CDT).sup.1/2 /BW

NTS in English units=0.060×the NTS in the above defined metric units.

Tissue Making Process

The oil containing enzyme modified fibers of the present invention maybe used in any commonly known papermaking process for producing, soft,bulky, sanitary paper webs such as tissue, towel, napkins and facialtissue. Many different papermaking processes including those processeswherein the web is dried via can drying, through drying, thermal drying,and combinations thereof are suitable. Exemplary of the types ofpapermaking processes which might be used in conjunction with thepresent invention are those processes taught in U.S. Pat. No. 3,301,746to Sanford et al., U.S. Pat. No. 3,821,068 to Shaw, U.S. Pat. No.3,812,000 to Salvucci et al., U.S. Pat. No. 3,994,771 to Morgan, Jr. etal., U.S. Pat. No. 4,102,737 to Morton, U.S. Pat. No. 4,158,594 toBecker et al., U.S. Pat. No. 4,440,597 to Wells et al., and U.S. Pat.No. 5,048,589 to Cook et al.

The preferred papermaking process is commonly known as the dry crepeprocess. Generally this involves using the paper furnish of the presentinvention to which dry strength chemicals are preferably added togenerate tensile strength and other papermaking chemicals may be added.The paper furnish is then pumped from a machine chest and flows to aheadbox and through a slice at 0.1 to 0.4% consistency onto a horizontalsurface of a Fourdrinier wire through which water is withdrawn and webformation takes place. The wire cloth is entrained around a breast rolland several table rolls, then to a wire turning roll from which it isfed around a couch roll and several guide rolls back to the breast roll-One of the rolls is driven to propel the Fourdrinier wire. One or morevacuum boxes, deflectors or hydrofoils may be used between the tablerolls to enhance water removal.

The wet web is formed on the upper surface of the Fourdrinier andtransferred to a felt by pressing the web onto the felt by means of acouch roll or transferring the sheet to The felt by means of a pick-upshoe. The felt transports the web to a press assembly. The felt thenmoves around one or two press rolls, one of which may be a suction roll,and then is entrained around guide rolls and rotates back to the couchroll. Showers and guard boards can be used at various positions on thefelt surface to assist in web pick-up, cleaning and conditioning thefelt surface. The press assembly comprises either a single press roll oran upper and lower press roll. Moisture is removed in the nip of thepress assembly and transferred into the felt.

The formed and pressed web is transferred to the surface of a rotatingdrying cylinder, referred to as a yankee dryer. The drying assembly mayalso include a hot air hood surrounding the upper portion of the yankeecylinder. The hood has hot air nozzles which impinge on the web andassist in moisture removal. The hood includes an exhaust to remove airfrom the hood chamber to control temperature. The web is removed fromthe drying surface using a doctor blade to impart crepe to the web. Toassist in removing the web from the drying surface in a controlled,uniform state, a creping adhesive is applied to yankee surface using aspray system. The spray system is a series of spray nozzles attached toa header pipe extending across the width of the dryer surface. Thecreping adhesive can be any of the types commonly used in tissuepapermaking technology.

The paper web creped from the drying cylinder is passed through a nipformed by a pair of rolls and wound into a large roll referred to as aparent roll.

The tissue making process used in the examples can be generallycharacterized as a light weight, dry crepe process. A 14 inch wide pilotplant scale machine was operated as follows: Prior to web formation thepaper furnish is contained in a machine chest where dry strengthadditives, dyes or other chemical additives are incorporated. The paperfurnish is delivered via a fan pump which flows from a headbox through aslice at 0.1% to 0.4% consistency onto the horizontal surface of aFourdrinier wire through which water is withdrawn and web formationtakes place. The wire is entrained around a suction breast roll whichaids in water removal and web formation. The wire is entrained aroundseveral guide rolls and a wire turning roll and is fed back to thebreast roll. One of these rolls is driven to propel the Fourdrinierwire.

The wet web is formed on the upper surface of the Fourdrinier andtransferred to a felt by means of a vacuum pick-up. The felt transportsthe sheet to a pressure roll assembly. The felt moves around onepressure roll, a solid rubber roll, and is entrained around guide rollsand rotates back to the vacuum pick-up. Moisture is removed in the nipof the pressure roll and transferred into the felt.

The formed web is pressed and transferred to the surface of a rotatingdrying cylinder, commonly referred to as a Yankee Dryer. The web isremoved from the surface of the Yankee at a web dryness between 95% and96% using a doctor blade. To assist in removing the web from the dryersurface in a controlled uniform state, a creping adhesive is applied tothe Yankee surface using a spray nozzle. The adhesive mixture used inthese examples was a 70/30 mixture of 70% polyvinyl alcohol and 30% of astarch based latex (National Starch Latex 4441).

The paper web creped from the drying cylinder was passed through a nipformed by a pair of rolls and wound into a parent roll of desired sizefor testing. The paper machine formed a web 14 inches wide and ran at areel speed of 40 to 50 feet/minute. All of the dry creped tissue samplesin the examples were produced at a basis weight of 10 pounds/ream and18-20% crepe. The samples were converted to 2-ply tissue (20pounds/ream) for all testing.

The synergistic result from the combination of oils, coarse fibers andsurfactants is demonstrated in the following examples. All proportionsused herein are by weight unless otherwise specified and fiber weight isbased upon the air dried weight of the fiber unless otherwise indicated.

EXAMPLE 1

Before the sample tests and results are described, it may be helpful tounderstand the data in Table I. The first column labeled,"SAMPLE/NUMBER", lists samples 1a through 1o. It should be noted thatsamples 1a through 1k are samples 3a through 3k, which come from TableIII that were tested in of U.S. patent application Ser. No. 08/268,232,filed on Jun. 29, 1994. Samples 1a through 1k are incorporated intoTable I for comparison purposes.ll

A fiber mixture was prepared having 100% virgin fibers of the type usedto make newsprint in the United States. The pulp sample contained 60%low freeness (about 250° CSF) softwood chemi-thermomechanical pulp(SWCTMP), 30% softwood stoneground pulp and 10% northern softwood kraftpulp. This 60/30/10 blend of virgin fibers was selected to simulate theblends found in newsprint. Virgin fibers were employed because they donot contain any contaminants introduced in the manufacture ofnewspapers. The pulp was formed into a sheet of flat paper and driedwithout any chemical additions. The flat paper was divided intorepresentatives samples and, separate papermaking furnishes wereprepared from each flat paper sample and dry creped tissue product wasproduced from each flat paper furnish sample on a 14" wide dry crepetissue machine as described above.

The samples of flat paper were designated samples 1N and 1O. Whilesample 1N was left uncontaminated, sample 1O was contaminated withsurfactant and with enzymes, dewatered to a consistency of about 25-35%;crumbed to produce crumbed fiber; and passed through a fiber disperserand mixed with 0.50-2% soy bean oil while the fiber temperature wasmaintained at about 180° F. by injected steam, before being repulped andmade into lightweight dry crepe tissue. Lightweight dry crepe tissueproducts were made from each of the samples 1N and 1O: A separate pulpslurry was prepared with each tissue sample. A cationic starch drystrength resin Solvitose®--N (available from Nalco Chemical Co.) wasadded at a rate of 1% of the fiber weight. The pulp slurry at about 6%consistency was elevated to a temperature of 180° F. for 15 minutes.After being pulped and held at the elevated temperature for 15 minutes,the pulp slurry made from the sample (soy bean oil contaminated) wascooled to about 140° F., and diluted to a consistency of 5%, and the pHwas reduced from ambient pH obtained with just pulp and tap water to apH of 5 by the slight addition of sulfuric acid. Surfactant and anenzyme mixture of cellulase enzyme (Celluclast 1.5 L, Novo NordiskBioindustrials, Inc.), xylanase (Pulpzyme HA, Novo NordiskBioindustrials, Inc.) and resinase (Resinase A 2X, Novo NordiskBioindustrials, Inc.) was added to the 5% consistency furnishes ofsample 1O. The enzyme addition uses 66.5 ml cellulase to 16.5 mlxylanase and 16.5 ml resinase per 100 lbs of air dried pulp. Afteraddition of the enzymes, the pulp slurry of sample 1O was held at about140° F. for 30 minutes with mild agitation and then cooled and adjustedto pH 7 with sodium hydroxide raised.

The pulp was dewatered to a consistency of 25-35%. The dewatered fiberswere then crumbed and then passed through a fiber disperser and mixedwith the soy bean oil, while the fiber temperature was maintained atabout 180° F. by injected steam.

The pulp slurry was then used to make lightweight dry crepe tissue asdescribed above. Significant softness in terms of handfeel for thissample was observed. A substantial, synergistic improvement in softnesswas obtained by the combination of oil contamination of the fibers and atreatment with the enzymes. Table I gives the results of the NormalizedTensile Strength (basis weight and directionally normalized) andhandfeel for the tissue samples 1N and 1O. It can be seen from the tablethat dramatic improvement in handfeel (perceived softness) is achievedby the combination of enzyme treatment and oil contamination viadispersing treatment with steam on the tissue product.

EXAMPLE 2

Three pulp furnishes made from different sources of high coarsenessfibers were treated and made into lightweight dry crepe tissue productusing the same papermaking procedures as in Example 1. Two tissuesamples designated 1K and 1L were made from a pulp obtained fromrepulping old newspaper (ONP). The other tissue sample, designated 1Mwas made from 70% ONP and 30% flexo newsprint. All tissue samples werefirst made by slurrying the pulp with water at 6% consistency. Theslurry was raised to a temperature of 180° F. and maintained at theelevated temperature for 30 minutes.

Each of the pulp slurries from samples 1K, IL and IM, were subjected toan additional treatment prior to being used in the papermaking process.This additional treatment was comprised of reducing the temperature ofthe pulp slurry from 180° F. to 140° F., adjusting the pH with sulfuricacid to 5.0 and adjusting the consistency to 5% adding surfactant andenzyme mixture. The enzyme addition was at a rate of 66.5 ml. forcellulase, 16.5 ml. xylanase and 16.5 ml. for lipase per 100 pounds ofpulp, and the enzymes were added to the 140° F., 5% consistency slurriesto be used for making these tissue samples. After the enzyme treatment,the slurry was dewatered to a consistency between about 25-35%. Thedewatered pulped fiber was then crumbed to produce crumbed fibers. Thecrumbed fibers from samples 1L and 1M were then passed through a micar.

Sample IL was mixed with 1% of mineral oil while the fiber wasmaintained at a temperature of about 180° F. by injected steam.

Sample IM, made from 70% oil/30% flexo newsprint was mixed with 1.0% ofmineral oil while the fibers were maintained at a temperature of about180° F. by injected steam.

The 5% consistency slurries for all samples were then maintained at 140°F. for 30 minutes, cooled, adjusted to pH 7 with sodium hydroxide andused as furnish for making dry crepe tissue with the papermakingequipment and process described in Example 1. The cationic dry strengthresin Solvitose® N was added to the furnish at a rate of 1% based on theweight of fibers. Tissue samples 1K, 1L, and 1M were then tested forhandfeel, tensile in both machine and cross machine direction and forbasis weight. The results are shown in Table I. The tensile and basisweight data were used in the mathematical calculation of thedirectionally normalized tensile strength (NTS). The results establishedthe benefits of the addition of oils and steam to fibers of coarsenessof 17 mg/100 meters and higher after enzyme treatment.

EXAMPLE 3

Two tissue samples designated A and B were prepared from a pulp obtainedby repulping old newspaper. Both tissue samples were first made byslurrying the pulp with water at 6% consistency. The slurry was raisedto a temperature of about 180° F. and maintained at the elevatedtemperature for about 30 minutes.

Each of the pulp slurries were subjected to an additional treatmentprior to being used in the papermaking process. This additionaltreatment was comprised of reducing the temperature of the pulp slurryfrom 180° F. to 140° F., adjusting the pH with sulfuric acid to 5.0 andadjusting the consistency to about 5.0%. A surfactant and an enzymemixture consisting of 66.5 ml, of cellulase 16.5 ml. xylanase and 16.5ml. lipase was added per 100 pounds of pulp at 140° F. After the enzymetreatment, the slurry was dewatered to a consistency between about 25%to 35%. The dewatered pulped fiber was then crumbed to produce crumbedfibers. The crumbed samples were then passed through a disperger.

Sample A was mixed with 1% of mineral oil while the fiber was maintainedat a temperature of about 180° F. by injected steam, whereas sample Bwas mixed with castor oil while the fiber was maintained at 180° F. byinjected steam.

The dewatered samples were then adjusted to a consistency of 5% and usedas furnish for making dry crepe tissue with the papermaking equipmentand process described in example 1. Tissue samples A and B were thentested for handfeel, tensile, both machine and cross direction and basisweight. The tensile and basis weight data were used in the mathematicalcalculation of directionally normalized tensile strength. These resultsare listed in Table II. The results show that the type of vegetable oilused in the disperger has a significant effect on the softness. Thecastor oil is preferred to the mineral oil.

EXAMPLE 4

A fiber mixture was prepared using 100% virgin fibers of the type usedto make newsprint in the United States. The pulp mixture contained 60%low freeness (about 250 CSF) softwood chemi-thermomechanical pulp(SWCTMP), 30% softwood stonegroundwood pulp and 10% northern softwoodkraft. This 60/30/10 blend of virgin fibers was selected to simulate theblends found in newsprint. Virgin fibers were employed because they donot contain any contaminants introduced in the manufacture and printingof newspapers. Dry creped tissue samples were prepared at two differenttensile levels on a 14" wide dry crepe tissue machine as describedabove. These samples are designated A1 through A4 in Table III.

Four pulp furnishes, Samples B, C, D and E, of old newspaper wereprepared at 5% consistency, dewatered to a consistency of 25 to 25% andthen crumbed Sample B was passed through a fiber disperger and mixedwith mineral oil but was not subjected to steam treatment. Sample C waspassed through a disperger and subjected to steam treatment at 180° F.but was not mixed with oil. Samples D and Sample E were passed through adisperger and mixed with 0.5 to 2.0% of mineral oil while the fibertreatment was maintained at 180° F. with steam.

The four treated furnishes were separately slurried to a consistency of5% and subjected to enzyme treatment as described in Example I.

The enzyme treated samples were then used as furnish for making drycrepe tissue and the papermaking equipment described in example 1.

Sample D and Sample E were passed through the disperger and mixed withoil and subjected to steam treatment and prepared at two differenttensile levels.

Tissue samples A through E were tested for handfeel, tensile, bothmachine and cross direction and basis weight. The tensile and basisweight data were used in the mathematical calculation of directionallynormalized tensile strength.

The results in Table III show that Sample B through D had better insoftness levels than the controls at equivalent NTS.

We claim:
 1. A method of making sanitary paper products from cellulosic fibers, comprising:(a) pulping said cellulosic fibers in water with agitation to produce a pulp slurry, said slurry having a consistency between about 3% to about 18% and a pH below about 8.0; (b) adding to the slurry a surfactant and at least one enzyme selected from the group consisting of cellulase, hemicellulase and lipase and maintaining said pulp slurry at a temperature above about 100° F. for at least 15 minutes; (c) dewatering the slurry to a consistency of from about 25% to about 35%; (d) crumbing the dewatered slurry, thereby producing crumbed fiber; (e) passing the crumbed fiber through a fiber disperser and mixing oil selected from the group consisting of vegetable oil, mineral oil, lanolin oil, and their derivatives thereof with said fiber to produce treated pulp containing oily products; and (f) forming said treated pulp into a wet web and drying the web to form a sanitary paper product.
 2. The method of claim 1 wherein said cellulosic fibers are high coarse fibers having a coarseness of greater than 17 mg/100 meters.
 3. The method of claim 1 wherein said cellulosic fibers are low coarse fibers having coarseness of less than 17 mg/100 meters.
 4. The method of claim 1 wherein said hemicellulase is xylanase.
 5. The method of claim 1 wherein the sanitary paper product is a tissue paper made at a basis weight between 7 and 35 pounds per ream.
 6. The method of claim 1 wherein the sanitary paper product is a paper towel made at a basis weight between 20 and 40 pounds per ream.
 7. The method of claim 1 wherein said pH of said pulp slurry is maintained between about 4 and
 7. 8. The method of claim 1 wherein said pH and chemical additions to the pulp slurry are insufficient to saponify said oily components.
 9. A method of making sanitary paper products from cellulosic fibers comprising:(a) pulping said fibers in water with agitation to produce a pulp slurry, said slurry having a consistency between about 3% and 18% and a pH below about 8.0; (b) maintaining said pulp slurry at a temperature above about 100° F. for at least 15 minutes; (c) adding to the slurry at a temperature below 140° F. a surfactant and at least one enzyme selected from the group consisting of cellulase, hemicellulase and lipase; (d) maintaining said pulp in contact with said enzyme for at least about 30 minutes; (e) dewatering the slurry to a consistency from about 25% to about 35%; (f) crumbing the dewatered slurry, thereby producing crumbed fibers; (g) passing the crumbed fibers through a fiber disperser, and mixing oil selected from the group consisting of vegetable oil, mineral oil, lanolin oil and derivatives thereof with said fiber to produce treated pulp containing oily product, and maintaining said fibers at a temperature of about 180° F.; and (h) forming said treated pulp into a wet web and drying the web to form a sanitary paper product.
 10. The method of claim 9 wherein said cellulosic fibers are high coarse fibers, having a coarseness of greater than 17 mg/100 meters.
 11. The method of claim 9 wherein said cellulosic fibers are low coarse fibers, having a coarseness of less than 17 mg/100 meters.
 12. The method of claim 9 wherein said temperature of said dispersed fibers in step (g) is maintained by injected steam.
 13. The method of claim 9 wherein said hemicellulase is xylanase.
 14. The method of claim 9 wherein the sanitary paper product is a tissue paper made at a basis weight between 7 and 35 pounds per ream.
 15. The method of claim 9 wherein the sanitary paper product is a paper towel made at a basis weight between 20 and 40 pounds per ream and is a paper towel.
 16. The method of claim 9 wherein said pH of said slurry is maintained between about 4 and
 7. 17. A method of making sanitary paper from high yield type cellulosic fibers comprising:(a) slurrying said cellulosic fibers with water at a consistency of between about 3% to about 18%; (b) adding surfactant and at least one enzyme to said slurry, said enzyme selected from a group consisting of cellulase, hemicellulase and lipase, and maintaining said pulp in contact with said enzyme for at least about 15 minutes; (c) dewatering the slurry to a consistency of from about 25% to about 35%; (d) crumbing the dewatered fiber, thereby producing a crumb fiber; (e) passing the crumbed fibers through a fiber disperser and mixing oil selected from the group consisting of vegetable oil, mineral oil, lanolin oil, and derivatives thereof with said fiber, and maintaining said fibers at a temperature of about 180° F. to produce a treated pulp; (f) forming said treated pulp into a wet web and drying the web to form a sanitary paper product; and (g) wherein said treated pulp is maintained below about a pH of
 8. 18. The method of claim 17 wherein said cellulosic fibers are high coarse fibers, having a coarseness of greater than 17 mg/100 meters.
 19. The method of claim 17 wherein said cellulosic fibers are low coarse fibers, having a coarseness of less than 17 mg/100 meters.
 20. The method of claim 17 wherein said temperature of said dispersed fibers in step (e) is maintained by injected steam.
 21. The method of claim 17 wherein said hemicellulase is xylanase.
 22. The method of claim 17 wherein the sanitary paper product is a tissue paper made at a basis weight between 7 and 35 pounds per ream.
 23. The method of claim 17 wherein the sanitary paper product is a paper towel made at a basis weight between 20 and 40 pounds per ream.
 24. The method of claim 17 wherein said pH of said pulp slurry is maintained between about 4 and
 7. 25. The method of claim 17 further comprising adding cationic dyes to said enzyme treated pulp.
 26. A method of making sanitary paper products from cellulosic fibers, comprising:(a) pulping said cellulosic fibers in water with agitation to produce a pulp slurry, said slurry having a consistency between about 3% and 18% and a pH below about 8.0; (b) adding to the slurry a surfactant and at least one enzyme selected from the group consisting of cellulase, hemicellulase and lipase and maintaining said pulp slurry at a temperature above about 100° F. for at least 15 minutes; (c) dewatering the slurry to consistency of from about 25% to about 35%; (d) crumbing the dewatered slurry, thereby producing crumbed fiber; (e) passing the crumbed fiber through a fiber disperser and mixing oil selected from a group consisting of vegetable oil, mineral oil, lanolin oil and derivatives thereof with said fiber to produce treated pulp containing oily products, and maintaining said fibers at a temperature of about 180° F.; and (f) forming said treated pulp with a wet web and drying the web to form a sanitary paper product.
 27. The method of claim 26 wherein said cellulosic fibers are high coarse fibers, having a coarseness of greater than 17 mg/100 meters.
 28. The method of claim 26 wherein said cellulosic fibers are low coarse fibers, having a coarseness of less than 17 mg/100 meters.
 29. The method of claim 26 wherein said temperature of said dispersed fibers in step (e) is maintained by injected steam.
 30. The method of claim 26 wherein said hemicellulase is xylanase.
 31. The method of claim 26 wherein the sanitary paper product is a tissue paper made at a basis weight between 7 and 35 pounds per ream.
 32. The method of claim 26 wherein the sanitary paper product is a paper towel made at a basis weight between 20 and 40 pounds per ream.
 33. The method of claim 26 wherein said pH of said pulp slurry is maintained between about 4 and
 7. 34. The method of claim 26 wherein said pH and chemical additions to the pulp slurry are insufficient to saponify said oily components.
 35. A method of preparing cellulosic fibers for making cellulosic sheets comprising:(a) pulping said cellulosic fibers in water with agitation to produce a pulp slurry, said slurry having a consistency of from about 3% to about 18% and a pH below about 8.0; (b) adding to the slurry a surfactant and at least one enzyme selected from the group consisting of cellulase, hemicellulase and lipase and maintaining said pulp slurry at a temperature above about 100° F. for at least 15 minutes; (c) dewatering the slurry to a consistency of from about 25% to about 35%; (d) crumbing the dewatered slurry, thereby producing crumbed fibers; and (e) passing the crumbed fibers through a fiber disperser and mixing oil selected from the group consisting of vegetable oil, mineral oil, lanolin oil, and derivatives thereof with said fiber to produce treated pulp containing oily products.
 36. The method of claim 35 wherein the enzyme is, xylanase.
 37. The method of claim 35 wherein the pH of the pulp slurry is maintained between about 4 and
 7. 38. The method of claim 35 wherein the pH and chemical additions to the pulp slurry are insufficient to saponify said oily components.
 39. A method of preparing cellulosic fibers for making cellulosic sheets comprising:(a) pulping said fibers in water with agitation to produce a pulp slurry, said slurry having a consistency of from about 3% to about 18% and a pH below about 8.0; (b) maintaining said pulp slurry at a temperature above about 100° F. for at least 15 minutes; (c) adding to the slurry at a temperature below 140° F. a surfactant and at least one enzyme selected from the group consisting of cellulase, hemicellulase and lipase; (d) maintaining said pulp in contact with said enzyme for at least about 30 minutes; (e) dewatering the slurry to a consistency of from about 25% to about 35%; (f) crumbing the dewatered slurry, thereby producing crumbed fibers; and (g) passing the crumbed fibers through a fiber disperser, and mixing oil selected from the group consisting of vegetable oil, mineral oil, lanolin oil, and derivatives thereof with said fiber to produce treated pulp containing oily products, and maintaining said fibers at a temperature of about 180° F.
 40. The method of claim 39 wherein the temperature of the dispersed fibers in step (g) is maintained by injected steam.
 41. The method of claim 39 wherein the hemicellulase is xylanase.
 42. The method of claim 39 wherein the pH of said slurry is maintained between about 4 and
 7. 43. A method of preparing cellulosic fibers for making cellulosic sheets comprising:(a) slurrying said cellulosic fibers with water at a consistency of from about 3% to about 18% to produce a pulp slurry; (b) adding surfactant and at least one enzyme to said slurry, said enzyme selected from a group consisting of cellulase, hemicellulase and lipase, and maintaining said pulp in contact with said enzyme for at least about 15 minutes; (c) dewatering the slurry to a consistency of from about 25% to about 35%; (d) crumbing the dewatered fiber, thereby producing crumbed fibers; (e) passing the crumbed fibers through a fiber disperser and mixing oil selected from the group consisting of vegetable oil, mineral oil, lanolin oil, and derivatives thereof with said fiber, while maintaining said fibers at a temperature of about 180° F. and a pH below about 8, to produce treated pulp containing oily products.
 44. The method of claim 43 wherein the temperature of the dispersed fibers in step (e) is maintained by injected steam.
 45. The method of claim 43 wherein said hemicellulase is xylanase.
 46. The method of claim 43 wherein the pH of the pulp slurry is maintained between about 4 and
 7. 47. The method of claim 43 further comprising adding cationic dye to said enzyme-treated pulp.
 48. A method of preparing cellulosic fibers for making cellulosic sheets comprising:(a) pulping said cellulosic fibers in water with agitation to produce a pulp slurry, said slurry having a consistency of from about 3% to about 18% and a pH below about 8.0; (b) adding to the slurry a surfactant and at least one enzyme selected from the group consisting of cellulase, hemicellulase and lipase and maintaining said pulp slurry at a temperature above about 100° F. for at least 15 minutes; (c) dewatering the slurry to a consistency of from about 25% to about 35%; (d) crumbing the dewatered slurry, thereby producing crumbed fibers; and (e) passing the crumbed fibers through a fiber disperser while maintaining the fiber at a temperature of about 180° F. and mixing oil selected from the group consisting of vegetable oil, mineral oil, lanolin oil, and derivatives thereof with said fiber to produce treated pulp containing oily products.
 49. The method of claim 48 wherein said hemicellulase is xylanase.
 50. The method of claim 48 wherein the pH of the pulp slurry is maintained between about 4 and
 7. 